The present invention relates to an improvement in a single lens enlarger for producing autostereoscopic pictures on a lenticular print film.
In producing a three-dimensional print, a series of photographs are taken of the subject field from differing angles of view. The negatives in the series are printed on film covered with a lenticular screen to form lineiform images of the subject. The exposed film is developed and covered with a lenticular viewing screen such that from any given viewing angle the screen projects, through the lenslets, a composite image of only one of the negatives. Since the eyes of a person viewing the screen are disposed at two spaced viewing angles relative to the screen, the screen projects two different composite images to the eyes, corresponding to two different viewing angles of the subject field and thus produces a stereoscopic image.
To print the negatives in the series, the area beneath each lenticule is divided into a number of equal segments corresponding to the number of negatives in the series. The first negative in the series is aligned with a projecting lens such that the image, which is laterally condensed by the lenticules into a narrow band, falls upon and exposes the film only in the designated segment area below the lenticules of the lenticular screen. This process is repeated for each negative in the series to fill in the remainder of segments below each lenticule. Alternatively, a plurality of projecting lenses may be arranged such that all the negatives are projected simultaneously onto their respective segments below the lenslets.
Once the negatives have been printed on the photographic paper, a lenticular viewing screen is applied to the print. For any given viewing angle, the lenticules of the screen project and enlarge only a portion of the film below each lenticule, which may be a segment or less than a segment. The portion projected by each lenticule corresponds to the same photograph in the series such that the projected and enlarged portions form a continuous, composite photograph. When the screen is viewed from a different viewing angle, a different portion of the print below each lenticule, corresponding to a different photograph in the series (and thus a different viewing angle), is projected and enlarged to form another continuous, composite photograph. Accordingly, when the screen is viewed simultaneously from two different viewing angles, as occurs when a viewer looks at the screen through both eyes, different composite images, representative of two different angles of view of the subject field, are projected to each eye, and the print appears to be three-dimensional.
In three-dimensional printing processes, when each negative in the series is projected onto a segment of lenticular film, the focal width of the laterally condensed image is such that the projected image on the film does not occupy the entire segment, but takes up only a small part of the designated segment. In order to avoid gaps between segments, apparatus is provided for expanding the individual, projected, condensed lineiform images to fill in the remaining area of the designated segment, such that the images in the segments will be contiguous (but do not overlap). This is accomplished by "scanning" the projected image from each frame in a direction transverse to the longitudinal direction of the lenticules. The scanning movement may either be continuous or be intermittent.
Preferred methods and apparatus for carrying out the scanning process are disclosed in U.S. Pat. No. 3,953,869, the pertinent portions of which are hereby incorporated into the present application. As there disclosed, for each negative in the series, the negative is first positioned in front of the light gate so as to be aligned with the projecting lens. The lamp is turned on behind the negative, to project the negative image through the light gate and projecting lens onto the lenticular screen. Each lenslet of the screen condenses the image incident thereon into a narrow band and directs the band onto a portion of the unexposed film. The projecting lens is positioned such that the band falls within the pre-assigned segment. The film, light source and projecting lens are thereafter moved synchronously, either continuously or intermittently, to scan the film and fill in the remaining area of the segment.
Once the segment is filled, the light source is turned off by closing a shutter and is stopped, and the negative carrier is shifted to move the first negative in the series out of the light gate and position the second negative in the series in front of the light gate. The negative carrier is then adjusted to align the key subject matter of the second negative with that of the first. The light source is again turned on, and the light source, negative, and projecting lens are moved synchronously, either continuously or in steps, to scan the second segment below each lenticule. This process is repeated for the remaining negatives in the series until all the segments under each lenticule are filled.
The foregoing apparatus is advantageous in that a single lens projector may be employed, and the ability of the negative carrier to handle a series of attached negatives permits the machinery to be fully automated, including the feeding and withdrawal of film strips to and from the film strip carrier, and the feeding and withdrawal of lenticular film to and from the exposure station.
In the foregoing arrangement, while scanning each segment the light source is moved along with the travelling negative and lens to provide adequate exposure light intensity. The light source is mounted behind the negative which is positioned in front of the light gate, and is synchronously driven with the negative and projection lens housing during scanning. As described above, however, there are a number of stop and move periods in one complete printing cycle. Each time a segment has been scanned, the projecting lens, film carrier, and light source are stopped until the next negative is positioned in front of the light gate and the key subject area is aligned. Jerking due to rapid stop and start of the lamp housing increases the chance of reducing the lifetime of the projection lamp, and therefore is undesirable. Also, where the lamp and projection lens are contained in essentially a common housing, to move synchronously the mass of the housing that must be stopped and re-started for scanning is increased.